Relationship of Podoplanin and Glutathione S-transferases T1 Expression with Laryngeal Cancer

The aim of this study is to determine whether there is a role of podoplanin and glutathione S-transferases T1 (GST-T1) expression in laryngeal squamous cell carcinoma. The study was completed with 33 patients and gene expression analysis was performed by qRT–PCR. The podoplanin and GST-T1 expression patterns were analyzed to determine their correlation with clinicopathologic parameters of laryngeal cancer. Of all patients, 20 had supraglottic, and the remaining 13 had glottic laryngeal cancer. Increased expression of podoplanin was found in 14 tumor tissues, but GST-T1 expression was not detected. Podoplanin expression did not show any prediction for regional metastasis, thyroid cartilage invasion, lymphatic vessel invasion or tumor differentiation for laryngeal cancer, also there were no significant differences in podoplanin expression between glottic and supraglottic regions, but extracapsullar extension is almost statistically significant (p=0,05).

In addition, patients with lymph node metastasis and upregulated podoplanin expression had shorter disease-specific survival rate than other patients.
According to the diagnosis, 25 % of cases have regional and 8-10% have distant metastasis (17,18). Podoplanin is frequently expressed in cutaneous head and neck squamous cell carcinoma (HNSCC) and may serve as predictor for regional lymph node metastasis, locoregional recurrence, and clinical outcome (19).  (23). They comprise four classes of genes (α, µ, π, and θ) and each class includes various genes (24). GST family consists of different classes of enzymes. GST-T1 enzyme in GST T class has its gene located on chromosome 22q11.2 (25,26).
It has been shown that individuals carrying the null genotype of GST have significantly reduced activity of this antioxidant enzyme (27,28) and so have higher levels of intermediates of oxidative metabolism. This genotype is related with many diseases (29,30). The revealed alterations in expression of GST-T1 enzyme can cause activation of carcinogenic particles or extinction of toxic effects. Therefore, it is thought that GST-T1 enzyme may be an important biomarker for diagnosis of laryngeal cancer. The aim of the study is to determine whether there is a role of podoplanin and GST-T1 in laryngeal SCC.

Statistical analysis
All statistical analyses were performed using the SPSS version 13.0. The relationship between the podoplanin expression statuses and clinicopathologic parameters was analyzed using the Pearson's chi-square test or Fisher's exact test.
All tests were two-sided, and the P values less than 0.05 were considered statistically significant.

Results
Tissue samples were obtained from 42 patients with laryngeal carcinoma, but the tissues of 9 patients were excluded from the study because of technical reasons. Therefore, the study was completed in 33 patients whose mean age±SD was 58.03±11.10 years. All patients were male. Thirtyone patients were smokers, whereas tree patients used alcohol regularly (Table 1). Of all, 20 patients had supraglottic, and the remaining 13 had glottic laryngeal SCC. Podoplanin overexpression was found in 14 patients and on the other hand decreased podoplanin expression was found in 19 patients (Fig.1). The association between the patient characteristics and their podoplanin expressions was shown in (Table 2). GST-T1 expression was not detected.   Rodrigo et al. found that podoplanin expression was related with regional metastasis that is also supported by our study (34). However, no statistically significant difference about the tumor site was found. Regional lymphatic metastasis observed was two fold higher in patients with low podoplanin expression level than in patients with high podoplanin and may serve as a predictor for lymph node metastasis and poor clinical outcome (35).
It is well known that the most prognostic factor of laryngeal cancers is regional lymphatic metastasis. Regional metastasis may be related with lymphangiogenesis. For this reason, it was aimed to find if podoplanin expressed on lymphatic vessels but not on the capillary vessels, can be used for the prediction of regional metastasis. Völker et al.
reported that the podoplanin expression did not show significant advantages for the prediction of sample (44)(45). Therefore, GST-T1 gene expression was investigated in the study. However in the present work GST-T1 expression was not observed. many biomarkers were found to determine the prognosis or metastatic disease of many malignancies, but no biological marker was found yet for determination of the survival rate or metastatic disease for laryngeal cancer.